Breaking Free from the Periodic Table

This week, Columbia’s Cory Dean has been awarded a 2023 Brown Investigator Award from the Brown Science Foundation, a nonprofit that supports scientific discovery. The award recognizes mid-career scientists for their curiosity-driven research in physics and chemistry.

“We were delighted to learn that Cory Dean’s discovery work in quantum materials will be supported by the Brown Foundation,” said Dmitri Basov, Physics Department Dean and Task Lead of the Columbia Quantum Initiative. “Remarkably, this is the second year in a row that quantum scientists at Columbia Physics have been recognized.” Last year, Tanya Zelevinsky was selected for her work on ultracold molecules.

Dean received his PhD from McGill University in Montreal before joining Columbia Engineering as a postdoc in 2009. During his postdoc, he helped develop a new technique to improve experimental devices made from graphene, a carbon-based material that can be stacked and combined with others to produce unique quantum phenomena, like superconductivity and magnetism. Dean joined the Physics Department faculty in 2014.

Today, Dean’s lab studies the electronic properties of quantum materials like graphene, with a focus on how electrons behave in materials that are just one atom thick. The electronic properties of any material are determined by the specific atoms that make it up and how those atoms are arranged.  By reducing dimensionality—in other words, making materials extremely thin—and changing the type and arrangement of the atoms in a material, new quantum properties can be realized.  However, not all materials remain stable when they are that thin, and natural atoms, i.e. those found on the periodic table, tend to arrange into particular patterns.

With the support of the $2 million Brown Investigator Award, Dean wants to develop new and improved techniques to create artificial patterns of any shape or size that can yield different quantum properties on demand. He shared more on those plans, how quantum materials are changing materials science, and the satisfaction in bringing engineering and physics together.

What do you like about working with materials?

My dad was a machinist. I spent a lot of time growing up in his machine shop and have always gotten a lot of satisfaction out of seeing a design become a reality. When I was thinking about graduate school, I saw similar opportunities in condensed matter physics. My current work with quantum materials continues to explore the relationship between form and function but at the nano-scale, and I enjoy the amazing range of physics that intersects in the study of quantum matter, including classical and quantum mechanics, electromagnetism, thermodynamics, and even more exotic ideas like special relativity.  

The work in the lab also varies a lot day to day—there’s design work, mechanical work, electronic development, data acquisition and analysis, and more—and everyone from students to the principal investigator takes part in all aspects. That makes it fun and means there’s a huge opportunity for creativity. Plus, you can pursue both fundamental questions and potential applications.

You’ve co-authored over 300 research papers—do any stick out?

When I was a postdoc, I helped develop a technique to isolate graphene from its environment, which otherwise can obscure measurements of quantum behavior, by figuring out how to sandwich micron-sized sheets of graphene between another, complementary two-dimensional material called boron nitride. A few years later, we were able to use those devices to confirm the existence of a theoretical quantum behavior that was proposed three decades before, called Hofstader’s butterfly.

These two papers together articulate what I really like about working in this field. In the first, we were tackling a practical challenge—more engineering than physics. But it’s almost always the case that when we can meet technical challenges, we liberate new physics.

What physics do you hope to liberate with the Brown Award?

Despite the amazing variety of materials that can be grown or synthesized in the lab, materials science is fundamentally limited by the periodic table: Can you find in the earth a material with a property you want?  If not, can you mix available elements to build a desired new material?   

Recent breakthroughs in quantum materials are changing that. We can radically alter the behavior of a material simply by patterning it. This is a special feature of atomically thin, 2D materials:  imposing a periodic structure—known as a “superlattice”—on top of the existing atomic lattice alters how the electrons behave, and we can design artificial superlattices with shapes and symmetries that are not easily found with natural atoms.

There are some ways to do that already, like using electric fields to deflect electrons from certain regions in the material. There have also been exciting recent developments in the emerging field of “twistronics:” the resulting moiré pattern that forms when two lattices are stacked acts just like an artificial superlattice. 

The major technical challenge has been that these patterns have to be extremely small—at the 10-nanometer length scale—and have minimal disorder. We plan to explore a number of ideas to directly write patterns onto a material at the desired length scale, with low disorder, and that we could reconfigure in real time.

What could some of the consequences of that improvement be?

The really exciting opportunity here is that we could completely change the properties of a single 2D material on demand and in a reversible way simply by imposing uniquely sized and shaped patterns onto it. Imagine that you have a conductive material, like copper, but with a flip of a switch, you could turn it into glass—and back again. That kind of non-destructive, dynamic engineering would be amazing.

You’ve spent much of your career at Columbia—what’s unique about the environment here?

Columbia really fosters a lot of collaborations between schools and departments. For example, when I was a post-doc here, I was jointly appointed between a mechanical engineering and an electrical engineering lab, but I also spent a lot of my time working out of a physics lab. Now as a PI, I still collaborate closely with these departments, as well as others.  There are lots of opportunities for scientific exchange, which helps science move at a quick and exciting pace.

For students interested in joining you, what are you looking for?

In my career, I’ve worked in both engineering and pure physics labs. When I look for students, it’s not about their academic training—it’s about the attitude they bring. The work can be very challenging, and since we are often working right at the forefront of physics, we are often trying things no one knows how to do. That can be difficult to navigate, but also very exciting. It’s most important to be passionate and driven.